If you want to see how valid the point is, setup a national event on carpet with rubber mod, foam mod and 12th mod. See how many people rush to attend. My guess is that the attendance will not be the best, with most teams sending their mod teams and select few drivers that are competitive in super stock. Then there will be the few privateer stragglers to fill the back of the field.
My feeling is that there is the few that need to have their own class to have a chance to win. I honestly believe that those people are actually pretty sparce.
However, you also have those that know they cannot control a car at those speeds, or don't feel like doing a complete tear down and re-build between each run. Some know they can compete at the top level, only if they had the backing of the manufacturers in some capacity.
This leads to the question of why is there a super stock class (or intermediate)? At first the super stock class was intended for the amateurs to be able to move up and compete with the mod drivers. This was so they could test their chops against the best. However, spec class racing became highly competitive, and team supported. Super stock became the class where mod drivers could go to get extra track time.
Is there really too many classes? Think of SCCA and even local grass roots short track oval. Both types of racing have many divisions.
I think the real answer is that the promoter has to decide what divisions their national level event is going to showcase. NEGS is known to have only stock and super stock. IIC is known to only have 12th, WGT, sedan foam and rubber in various flavors. Birds has tons of everything.
Maybe it's time that promoters put their foot down and limited what classes/divisions they are going to run and not cave in to what the massive interweb junkies demand. Of whom most will not attend the race they are demand classes in.